1. Field of the Invention
The invention relates to a circuit protection device, more particularly to a circuit protection device that can effectively provide over-current and overheating protection to a main circuit.
2. Description of the Related Art
FIG. 1 illustrates a conventional circuit protection device 1 for providing over-current and overheating protection to a power supply system 2 that is used for supplying electric power to a peripheral circuit 21. The conventional circuit protection device 1 includes a current limiting circuit 11 connected to the power supply system 2 for limiting current through the power supply system 2 to a limited current value when the current through the power supply system 2 reaches a predetermined threshold value, and an overheat protecting circuit 12 connected to the power supply system 2 for shutting down the power supply system 2 when the operating temperature of the power supply system 2 reaches a predetermined value. Usually, the predetermined value is set to be within a range of 150° C.˜170° C. Hence, the overheat protecting circuit 12 shuts down the power supply system 2 once the operating temperature of the power supply system 2 reaches 150° C.˜170° C.
However, the predetermined value shifts as a result of differences between ideal and actual characteristics of components of the overheat protecting circuit 12 due to limitations in fabrication. For example, if the actual value shifts from an ideal value (such as 150° C.) to a lower value (such as 130° C.) or a higher value (such as 190° C.), the overheat protecting circuit 12 may inappropriately shut down the power supply system 2 even though the operating temperature of the power supply system 2 has yet to reach 150° C., thereby resulting in reduced efficiency; or the overheat protecting circuit 12 may fail to shut down the power supply system 2 when the operating temperature of the power supply system 2 exceeds 150° C., which can result in damage to the power supply system 2.